Fundamentally, the area of application of the invention encompasses all field devices employed as technical systems in the realm of automation technology that are directly associated with a production process. Such field devices can be actuators such as control elements or valves as well as sensors such as measuring transducers in production and process automation. The field devices are connected to a superordinated control system by means of a connecting line, usually via a field bus. This is used to exchange the data which then serves for purposes of regulation, control and further processing. Communication standards that are often employed for a field bus include CAN, HART, PROFIBUS, or else they can be configured on the basis of ETHERNET, Profinet, IP.
Moreover, these field devices, especially 4-20 mA devices, but also those with a field bus, are supplied with power via this connecting line.
In actual practice, the connecting lines do not run directly from the specific field device to the control component, but rather at first individually from the specific field device to a field device connection unit that is then connected to the control component via a power line, especially a bus line. German patent specification DE 101 35 980 C1 discloses an arrangement in which field devices that are situated decentralized and close to the process are connected to a remote central system in a technical automation installation with a distributor that has at least one communication interface for the communication with the remote central system, a plurality of pluggable I/O modules and a multi-pole terminal field for the connection of field devices. The I/O modules have a system-side communication interface and a field-side communication interface located in the same plugging plane. The system-side communication interfaces of the I/O modules are connected to the communication interface in order to communicate with the central system. The field-side communication interfaces of the I/O modules and the terminal field are connected to a plug contact device at contacts that are separate from each other.
In this context, a plug-in unit which determines the configuration is provided that has a corresponding mating plug contact device which mates with a plug contact device, and conductor bridges to electrically connect contacts of the plug-in unit that are separate from each other, in such a way that, in each case, a field device is connected to the field-side communication interface of at least one I/O module. In this context, an erroneous assembly of the system with the wrong plug-in units which determine the configuration can give rise to severe errors in the field device connection unit.
Consequently, there is a need to be able to test the field device connection unit. A drawback of the prior-art field device connection unit is that the field devices are connected to the field device connection unit via field wiring. Disconnecting and re-connecting the field wiring are very labor-intensive steps, in addition to which the re-connecting is prone to errors.